1. Field of the Invention
The present invention relates to the removal of water soluble organics (WSO) from oil process water, and more particularly to the removal of certain water soluble petroleum organics as well as non-hydrocarbon organic materials (NHOM) from crude oil production water and from aqueous streams used in removing water and/or organic salts, such as sodium chloride, from crude oil, residual oil, waste oils and the like.
2. Description of the Prior Art
In the removal of crude oil production fluid from earth formations, significant quantities of water are quite often removed along with the oil. In the Middle East, the production fluid can be virtually pure oil. However, it is not uncommon that oil well production fluids are composed of 90% or more of water and only 10% or less of crude oil. Such water is referred to as connate water and is produced along with the oil. One of the first steps after removal of the oil well production fluid is to separate the oil from the water by phase separation techniques. Separation is conventionally accomplished using a bulk separator or a free water knockout system. Virtually all of the hydrocarbon is conveniently recovered in this manner. Unfortunately, at some geographical areas, small amounts of oil (50-1,000 ppm) and salts of certain water soluble organic compounds, as well as inorganic salts and acids, are present. The water soluble substances are not removed when the production fluid is subjected to typical separation regiments. Water soluble organics include, among other things, certain naphthenates, phenols, lower fatty acids, etc. Water soluble inorganics salts include sodium chloride, sodium sulfate, calcium chloride, barium chloride, etc. While the amount of water soluble organics may be relatively small, up to 1,000 ppm (0.1%) or more, they nevertheless give rise to environmental problems, when the aqueous phase is discharged into the environment without removal of the water soluble organics. These organic products can complicate environmental concerns where this water is or can be discharged. Furthermore, the water soluble organics may be valuable substances. In order to meet the present day strict environmental standards, a process to reduce the level of water soluble organics in the discharged streams to 29 ppm or less is needed. Some known methods can reduce the content of water soluble organics to this level. For example, one could separate the water and water soluble organics by distillation or the use of biological treating ponds. However, such methods are relatively complex and/or expensive, requiring extensive periods of time to carry out these processes in comparison with the process of the present invention. U.S. Pat. No. 4,818,410 to Bellos (a co-inventor herein) et al. shows a less expensive and simpler technique. Nevertheless, increasingly stringent environmental standards may render it desirable, in some cases, to reduce the WSO content even further. The ability to achieve such reduction is beyond the capability of commercial methods if, for example, producers were required to reduce their organic levels in the discharge water to a much lower level such as 10 ppm.
Another method is disclosed in U.S. Pat. No. 5,104,545 to Means et al. This disclosure illustrates the great expense the industry is willing to incur for greater removal of water soluble organics. The method of Means et al. further involves problems with spoilation of the resin when it becomes oil wet and requires plentiful amounts of solvent or solvent regeneration. Further, these ion exchange resins are very expensive to employ.
Use of certain petroleum fuel oils for specific purposes requires that such oil be treated in order to remove undesirable corrosive contaminants therefrom. For example, fuel oils used in the newer, high efficient, gas turbine power plants must meet certain strict requirements with respect to the presence of inorganic contaminants in the oil. The presence of sodium chloride and other similar inorganic salts renders the oil less than suitable as a fuel in gas turbine power plants. To upgrade fuel oil so that it is acceptable for use in the turbines, the fuel oil is commonly processed using a multistage electrostatic desalting facility. In such operation, essentially complete removal of water soluble inorganic salts from fuel oil is accomplished by a counter current water washing process in which a high electrostatic gradient is used to break the interim water-in-oil emulsion. Selective specialized chemical demulsifiers are normally used in such salt removal processes. While the process removes the inorganic salts from the fuel oil, unfortunately, the wash water removes the water soluble organics from the fuel oil as well. In view of strict environmental standards, it is of considerable importance to remove these water soluble organics present in the wash water of the inorganic salt removal processes used to render the fuel acceptable for burning in turbines.
Thus, it is advantageous to provide a method that removes WSO's from oil well production fluids as well as from aqueous streams used to render fuel oil acceptable for use as fuel for gas turbine power plants. If these organic materials (WSO) are converted to their salts, such salts are even more destructive to the turbines. As noted, in U.S. Pat. No. 4,818,410 (Bellos et al), a method for removal of water soluble organics from oil process water and which is designed for such applications was disclosed. However, there is the ever present desire and the potential for further regulation to reduce the content of water soluble organics (especially non-hydrocarbon organic material) to an even greater extent.